In such a valve component group terminal or connecting ducts are formed in the terminal plate which on the one hand are able to be connected with a source of fluid under pressure, with loads or other means such as means for receiving expended fluid. On the other hand there is a connection with the ducts of a main valve, which has so far been mounted directly on the terminal plate. Using the main valve it is possible for some of the ducts to be connected with, or disconnected from each other fluidwise.
In this manner connected loads, as for instance actuator cylinders may be operated by supplying power fluid, more particularly compressed air. In order to operate the main valve there is as a rule at least one electrically operated pilot valve, more particularly in the form of a solenoid valve, operated by electrical power. So far this pilot valve has been mounted on the main valve so as to be able to influence the flow through a control duct by means of which the motion of the valve member of the main valve may be initiated.
The supply of electrical power to the pilot valve has so far been via electrical leads, which are left exposed and thus are liable to be damaged. Furthermore, when a valve is replaced the connections of the leads are liable to be confused through human error. The production of the electrical connections is also a relatively intricate operation. Therefore there has already been a proposal to supply the electrical power via the terminal plate. In this case it would then be necessary to mount the male and female parts of a plug connector on the terminal plate and the main valve and it would be necessary to provide extra space in order to make it possible to internally accommodate the wiring leading to the pilot valves. Such a design does however involve the disadvantage that the overall height of the main valve has to be substantially increased owing to the necessity of accommodating the associated parts of the plug connector. Normally the main valve comprises an elongated valve piston in it whose distance from the lower side of the valve would have to be increased. Another point is that the wiring channels lead to a further increase in the overall volume and to an increase in the manufacturing costs of the main valve, not to speak of the problem of insulation, for in order to exclude the possibility of shortcircuits a carefully thought out insulation system is required.